14C]PEG-4000, chloride, chloride/potassium and sodium spaces as indicators of extracellular phase volume in the tissues of rainbow trout, Salmo gairdneri richardson

Abstract

1. 1. Estimates of extracellular phase volume and cellular electrolyte concentrations based on [ 14C] PEG-4000, chloride, chloride/potassium and sodium spaces were compared at three epaxial muscle sites and in cardiac muscle, liver, gut, spleen and brain samples of rainbow trout. 2. 2. [ 14C] PEG-4000 appeared to provide realistic estimates of tissue water distribution and cellular ion levels in brain and is suitable for use with epaxial and cardiac muscle, gut and spleen but not liver. 3. 3. [ 14C] PEG-4000, chloride and chloride/potassium spaces were comparable in epaxial muscle, cardiac muscle and gut. Thus, no advantage is associated with use of the former rather than ion-defined estimates of extracellular phase volume in these tissues. 4. 4. [ 14C]PEG-4000 and sodium spaces appear to be preferable to chloride and chloride/potassium spaces as indicators of tissue water distribution in spleen. 5. 5. Sodium provides unrealistic estimates of extracellular phase volume in tissues other than spleen and liver.